Introduce a new temporary MDNode concept. Temporary MDNodes are

not part of the IR, are not uniqued, and may be safely RAUW'd.
This replaces a variety of alternate mechanisms for achieving
the same effect.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111681 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/DebugInfo.h

@@ -272,6 +272,10 @@ namespace llvm {
     StringRef getFilename() const    { return getCompileUnit().getFilename();}
     StringRef getDirectory() const   { return getCompileUnit().getDirectory();}
 
+    /// replaceAllUsesWith - Replace all uses of debug info referenced by
+    /// this descriptor.
+    void replaceAllUsesWith(DIDescriptor &D);
+
     /// print - print type.
     void print(raw_ostream &OS) const;
 
@@ -314,10 +318,6 @@ namespace llvm {
 
     /// dump - print derived type to dbgs() with a newline.
     void dump() const;
-
-    /// replaceAllUsesWith - Replace all uses of debug info referenced by
-    /// this descriptor.
-    void replaceAllUsesWith(DIDescriptor &D);
   };
 
   /// DICompositeType - This descriptor holds a type that can refer to multiple
@@ -654,6 +654,9 @@ namespace llvm {
                                         unsigned RunTimeLang = 0,
                                         MDNode *ContainingType = 0);
 
+    /// CreateTemporaryType - Create a temporary forward-declared type.
+    DIType CreateTemporaryType(DIDescriptor Context);
+
     /// CreateArtificialType - Create a new DIType with "artificial" flag set.
     DIType CreateArtificialType(DIType Ty);
 

include/llvm/Metadata.h

@@ -128,6 +128,16 @@ public:
                                        
   static MDNode *getIfExists(LLVMContext &Context, Value *const *Vals,
                              unsigned NumVals);
+
+  /// getTemporary - Return a temporary MDNode, for use in constructing
+  /// cyclic MDNode structures. A temporary MDNode is not uniqued,
+  /// may be RAUW'd, and must be manually deleted with deleteTemporary.
+  static MDNode *getTemporary(LLVMContext &Context, Value *const *Vals,
+                              unsigned NumVals);
+
+  /// deleteTemporary - Deallocate a node created by getTemporary. The
+  /// node must not have any users.
+  static void deleteTemporary(MDNode *N);
   
   /// getOperand - Return specified operand.
   Value *getOperand(unsigned i) const;